Polyisoprene of natural origin is a material useful for the manufacture of items for which it is desired to take advantage of the material's mechanical properties.
In particular, polyisoprene derived from plants differing from the rubber tree (Hevea) is increasingly being sought after, particularly to overcome the allergy problems encountered by users of items manufactured from Hevea-derived polyisoprene.
Polyisoprene extracted from plants differing from Hevea, particularly from guayule, is of particular advantage for preparing gloves e.g. medical or surgical gloves, or for condom production. After coagulation of the guayule latex, the polyisoprene obtained can also be used to produce items in rubber, in particular to manufacture tyres.
Methods are known for extracting polyisoprene from plants. In general, these methods use organic solvents.
For health and environmental reasons, the use of organic solvents must be restricted or else avoided.
The production of polyisoprene via aqueous phase extraction is also particularly advantageous from an economical viewpoint.
Methods are known for extracting polyisoprene in aqueous phase. However, these known methods do not allow high-quality polyisoprene to be obtained, in particular polyisoprene have a weight-average molecular weight (MW) possibly reaching 2 500 000 g/mol. Patent application US-2012/0063969 describes a method whereby guayule plants are milled under intense compression. The quality of the extracted polyisoprene may then be degraded. The amount of polyisoprene extracted from a given plant quantity and having satisfactory quality and weight-average molecular weight, (MW) is then reduced
In addition, known polyisoprene extraction methods do not always lead to obtaining polyisoprene in the form of a dispersion in water or in latex form.
Known aqueous phase extraction methods are generally implemented over particular pH ranges that are limited, generally strictly higher than 7 and in particular higher than 9, 10 or 11. Such pH values generally require the presence of a base substance which may lead to safety problems or which may lead to deterioration of the equipment used. Environmental pollution is also to be feared.